NitroX >>Now my question.

Who owns the term "Nitro Express"? I am not asking for any reason just interest. For example if a manufacturer wanted to bring out a 'new' Nitro Express could they? Perhaps the .400 and .465 H&H Magnums have also Nitro Express designations like the much earlier .375 H&H Magnum?

I would say the phrase has been used in so many contexts that I wouldn't think there would be any problem with useing the moniker on your wildcat!

There was one additional use of the term EXPRESS, was used in black powder rifles as well! That was long before the conversion to smokeless powder. The express versions of many black powder chamberings was the use of a lighter bullet to gain speed, and flatten trajectory. Most of these were singleshots, and double rifles to be used for hunting Roe deer, and stagg in Scotland/England, and Europe! The 500/450 #1 Express is one example of this use! It used 270 gr, and no larger than 365 gr bullets, when most 450 bores used 480 gr bullets! I have an old Westley Richards, so chambered, that was sold out of the London store in 1892! It is a hammerless box lock, with auto/sel ejectors, engraveing, in the maker's case!